The present invention relates to a recording-material such as pressure-sensitive recording paper, heat-sensitive recording paper, electro-heat sensitive recording paper, etc. More in detail, the present invention relates to a recording-material prepared by using a divinyl phthalide compound represented by the formula (I): ##STR2## wherein X.sup.1 represents an alkyl group, an alkoxy group or a halogen atom; X.sup.2 represents an alkyl group, an alkoxy group, a halogen atom or a group of R.sup.3 O--; X.sup.3 represents a halogen atom; R.sup.1 represents a hydrogen atom, an alkyl group, an alkoxyalkyl group, a haloalkyl group, an alkyenyl group, an aralkyl group, a cyclohexylmethyl group, a methylcyclohexyl group, a trimethylcyclohexyl group, a furfuryl group, a tetrahydrofuryl group or a tetrahydropyrane-2-yl-methyl group; R.sup.2 represents a cycloalkyl group, a phenyl group or a benzyl group having chlorine atom(s), bromine atom(s) or alkyl group(s) of not more than 4 carbon atoms as the substituent, or optional group R.sup.1 ; R.sup.3 represents a cycloalkyl group, an alkoxyalkyl group, an alkenyl group, a haloalkyl group, an aralkyl group or an aryl group; and m and n represent an integer of 0, 1, 2 or 3, respectively. When m and n are not less than 2, X.sup.1 of (X.sup.1).sub.m, X.sup.2 of (X.sup.2).sub.n or X.sup.3 of (X.sup.3).sub.4 can be same or different. (Hereinafter the same sign means the same meaning).
The divinyl phthalide compounds represented by the formula (I) are the novel compounds synthesized for the first time by the present inventors. The compounds are by themselves almost colorless, extremely stable in the atmosphere, have no subliming property and spontaneously chlomogenic property and dissolve extremely well in organic solvents. They give a blackish color rapidly by a developer and its color image is excellent in light-resistance and moisture-resistance. Furthermore, since the color image has a strong absorption between 700 and 1000 nm in addition of the visible region, the color image has a distinctive feature that it is possible to be read by the optical letter-reading apparatus using the near infrared rays (such as OCR and OMR) and the barcord reading apparatus. Namely, the divinyl phthalide compound of the present invention (hereinafter referred to as the present compound) is an extremely valuable and novel compound which can be used as a chromogenic agent for an ordinary recording-material developing black color, of which demand is rapidly increasing recently, as well as the material readable with OCR, OMR, etc.
The color image due to the black-coloring fluoran compound (A), which has been used as a conventional chromogenic agent for a recording-material, does not have any absorption in the near infrared region and accordingly, the color image could not be read by an optical letter-reading apparatus (refer to FIG. 2): ##STR3## (refer to Japanese Patent Publication No. 56-52759/1981).
On the other hand, as the chromogenic agents having an absorption in the near infrared region, some compounds have been recently proposed in Japanese Patent Publication No. 58-5940/1983, Japanese Patent Application Laid-Open (KOKAI) No. 59-199757/1984 and Japanese Patent Application Laid-Open (KOKAI) No. 60-230890/1985. However, each of the proposed compounds has the following defects and any satisfactory chromogenic agent has not been obtained in the present situation.
Namely, the compound (B) of Japanese Patent Publication No. 58-5940/1983 and the compound (C) of Japanese Patent Application Laid-Open (KOKAI) No. 60-230890/1985 have been themselves strongly colored in yellow and besides, they are strong in the spontaneous coloring. These defects have very had effect on production of the recording materials.
Although the fluorene compound (D) of Japanese Patent Application Laid-Open (KOKAI) No. 59-199757/1984 is colorless, the chromogenic property and the stability of color image are poor.
Furthermore, the hue of each of compounds (B), (C) and (D), when developed color, is green and accordingly, to obtain blackish color, another chromogenic agent giving red or black color must be added in a large amount, and since the chromogenic property and the chromogenic speed of each agent are different from those of compounds (B), (C) and (D) and particularly, the light-resistance of red-chromogenic agent is generally poor, bad influences such as unbalance of color-development and reduction of light-resistance could not be avoided. ##STR4## (refer to Japanese Patent Publication No. 58-5940/1983). ##STR5## (refer to Japanese Patent Application Laid-Open (KOKAI) No. 60-230890/1985). ##STR6## (refer to Japanese Patent Application Laid-Open (KOKAI) No. 59-199757/1984).
As a result of the present inventors earnest studies to improve the defects of the conventional chromogenic agents, the present invention has been attained.
The present invention has been attained by the present inventors who have found out that the divinyl compounds (I) are unexpectedly excellent in several properties such as the solubility, the coloring of the compound itself, the hue of the developed color, the chromogenic property, the absorbancy of near infrared rays and the stability of color image and have studied further the problems, and the present invention provides the compounds represented by the formula (I) and a chromogenic recording materials, which contains the compound (I) as a chromogenic agent.